The present invention relates to a cutting tool holder which circumscribes a longitudinal axis and is adapted for having coupled thereto at least one cutting tool, the cutting tool holder being of the type wherein there is relative rotational movement about such axis between the cutting tool and a workpiece.
FIG. 1 schematically depicts a prior art cutting tool holder 2 wherein a cutting tool is coupled thereto in a known manner. In particular, the cutting tool holder 2 comprises a housing 4 which includes a shaft 6 extending therethrough, the housing and shaft generally circumscribing a longitudinal axis 8. Shaft 6 is affixed to an end member 10 which is positioned within a cavity 12 of housing 4 for reciprocation along axis 8. End member 10 abuts a flanged portion of the housing 4. Cavity 12 is closed at one end by the end member 10 and at the other end by a cap 14. Shaft 6 extends within cavity 12 and is concentric with a spring 16 which bears against end member 10 and cap 14 to urge the end member and shaft affixed thereto in the direction of arrow 18. The end of shaft 6 which extends beyond housing 4 includes a generally cylindrical portion 20 to which is coupled a cutting tool 22 having a mating cylindrical bore 24 into which the cylindrical port1on 20 extends. During the cutting operation it is desirable to hold the cutting tool 22 in place relative to the cutting tool holder 2. It is to this end that spring 16 is provided to urge the end member 10 and shaft 6 in the direction of arrow 18 so that the cutting tool 22 is caused to bear against cap 14. When the cutting tool 22 is to be replaced, a force is exerted against the end member 10 in the direction of arrow 26 in a known manner causing the end member 10, shaft 6 and cutting tool 22 to move to the position shown in phantom lines in FIG. 1. In this position, the cutting tool 22 no longer abuts cap 14, and the cutting tool 22 can be removed from the cylindrical portion 20 of the shaft.
A problem incurred in such prior art cutting tool holders is that there is a tendency for the pressures exerted against the cutting tool during the cutting operation to move the shaft 6 in the direction of arrow 26 against the forces exerted by spring 16. In viewing FIG. 1, such pressures tend to move shaft 6 toward the right which removes the cutting tool 22 from abutting engagement with cap 14. The result of such movement is that the cutting tool 22 becomes undesirably loose relative to the shaft 6. This is particularly noticeable in milling and very heavy, large overhang turning or boring operations.
Although it might appear that this problem can be overcome by providing a spring 16 which exerts a very great force in the direction of arrow 18 of FIG. 1, the use of such a spring will cause other problems. For example, increasing the spring pressure of spring 16 will require a corresponding increase in the force required to remove the cutting tool when desired; that is, the force exerted against end member 10 and spring 16 in the direction of arrow 26. In this application where such opposite force is effected by hydraulic means, a relatively large hydraulic cylinder will be required. And, in apparatus wherein the cutting tool rotates to cut the workpiece, the result will be the exertion of undesirable forces upon the bearing structure causing premature wear and possible disorientation of the cutting tool.
It is highly desirable to provide a cutting tool holder wherein the cutting tool does not become loose during the cutting operation.
It is further desirable to provide such apparatus wherein the cutting tool can be positively locked into position relative to such holder and yet be readily removed therefrom when desired.
It is also desirable to provide such a cutting tool holder relative to prior art apparatus wherein less spring pressure is required to position the cutting tool relative to the holder.